1. Field of the Invention
The invention relates to semiconductor devices, particularly to a bridge rectifier embedded in an integrated circuit (IC), into which internal pads and an external bridge rectifier are integrated.
2. Description of the Related Art
In addition to detecting radio signals, rectifiers are used to convert alternating current (AC) signals into direct current (DC) signals, especially converting AC power into DC power.
FIG. 1 is a circuit diagram of a conventional bridge rectifier located outside an IC. Referring FIG. 1, a conventional bridge rectifier 100, located outside an IC 120, has four diodes D1, D2, D3 and D4 connected in a bridge arrangement to achieve full-wave rectification. A feature of the bridge rectifier 100 is that for both polarities of the input voltage (Vin1 with respect to Vin2), the polarity of the output voltage (VPX with respect to GND) is always constant. For example, when the voltage Vin1 is positive with respect to the voltage Vin2, two diodes D1 and D3 are forward biased and then current flows along the path La. When the voltage Vin1 is negative with respect to the voltage Vin2, two diodes D2 and D4 are forward biased and then current flows along the path Lb. As can be observed from the current paths La and Lb, the current flow through a load 120 is always in the same direction.
It is desirable to reduce hardware cost of conventional external bridge rectifiers. The invention addresses such a need.